Tetrahydrofuran (THF) is a cyclic ether, commonly used as a solvent. It is a borderline polar aprotic solvent, with a dielectric constant of 7.5 and dipole moment of 1.75 D (considerably less than those found for DMF, DMSO, acetonitrile and acetone). It is commonly used in Grignard reactions and in the formation of enolates with strong bases such as LDA.